This invention relates to a window frame construction for receiving and supporting a sliding window sash,, the frame to be mounted in a window opening in a wall of a structure, the window frame incorporating a J-rail return member to overlie siding applied to the exterior of the structure.
More particularly, the invention is directed to such a window frame that provides increased water resistance for a minimized exposed interior sill frame height and hence increased egress opening, the frame also providing increased stiffness or strength, resistance to impact, and reduced costs of material.
In the prior art there are many window frames which include a window retaining body portion for insertion into an opening in the wall of a building structure to circumscribe the interior of the opening and a nailing flange or fin circumscribing the exterior of the opening.
Many such window frames also include a J-rail return member or which comprises a nailing fin member, a member projecting outwardly from the nailing fin and a return member connected at the end of the outwardly projecting member. This J-rail return member defines a J-channel to receive the ends of siding or the like with the return portion of the J-rail return member overlying the siding. Such prior art window frames are disclosed in U.S. Pat. No. 2,983,001, issued May 9th, 1961, U.S. Pat. No. 4,694,612, issued Sep. 22nd, 1987, and U.S. Pat. No. 5,392,574, issued Feb. 28th, 1995.
When rain strikes the sliding sash or window unit, particularly when driven against the window unit by a strong wind, the water can penetrate between the sash and frame even with the sash tightly closed to collect under the sash where it drains off through openings at the bottom of the frame. Where the frame includes a J-return rail, the water flows out over the projecting portion of the J-return rail to spill over the end thereof.
The water resistance rating of the window, that is the amount of water forced against the window unit that can accumulate before it spills out over the inside of the sill of the window frame is determined by the height of the inside of the window frame at the window sill above the surface of the bottom of the frame or, in the case where the frame has a J-rail return, above the surface of the projecting portion of the J-rail return. The depth to which the water can accumulate before it spills over the inner edge of the frame is hereinafter referred to as the dam height.
If the inside height of the sill of the frame is increased, the dam height and hence water resistance of the window unit is increased. However, such increase in window frame height reduces the egress opening, that is the size of the opening through which a person can escape in the event of an emergency. In addition, increasing the height of the frame inner sill for increased dam height either by the frame profile itself or increasing the height of the sash retaining snap-in stop increases the amount of material required for the frame and hence the cost of the frame.
The present invention is directed to increasing the dam height without increasing the interior height of the sill thus providing for increased water resistance for the window unit without reducing the size of the egress opening. Further the invention provides such increased water resistance with minimal increase in material costs while affording increased frame stiffness or strength and resistance to impact.
This increased water resistance or dam height is achieved according to the invention by forming a section of the return portion of the J-rail return member with a double wall to provide a trough at the sill of the frame to receive water spilling over the projecting portion of the J-rail return member, the trough being provided with a discharge opening at the bottom thereof. With this arrangement, the dam height is the distance between the bottom of the trough of the J-rail return member and the inside height of the sill of the frame.
With this arrangement, the dam height increase is obtained without any reduction in the size of the egress opening presented by the frame, with the sash fully open.
Further by providing this double walled section of the return portion of the J-rail return member, the strength of the frame and its resistance to impact is significantly increased.